1. Field of the Invention
The invention relates to a terminal fitting with resilient contact pieces.
2. Description of the Related Art
Japanese Unexamined Utility Model Publication No. 3-55674 discloses a terminal fitting with opposite front and rear ends. A rectangular tube is formed at the front end of the terminal fitting and a resilient contact piece is in the rectangular tube. The resilient contact piece is supported at only one end and extends along forward and backward directions. A male tab inserted into the rectangular tube portion deforms the resilient contact piece. As a result, the male tab is pressed resiliently between a ceiling wall of the rectangular tube and the resilient contact piece with a specified contact pressure attributable to a restoring force accumulated in deformed the resilient contact piece.
The above-described terminal fitting could be miniaturized by reducing the thickness of the resilient contact piece. However the smaller resilient contact piece might not reliably achieve the specified contact pressure.
Two resilient contact pieces could be placed one over in an effort to increase the contact pressure. For example, FIG. 7 shows a terminal fitting with an upper resilient contact piece 101A that will contact a male tab (unillustrated) and a lower resilient contact piece 101B that will not contact the male tab. The two resilient contact pieces 101A, 101B are held in close contact with each other over substantially the entire length from base end portions 103A, 103B to extending end portions 102A, 102B. The extending end portion 102A of the upper resilient contact piece 101A is pressed by the male tab from above. Thus, both the upper and lower resilient contact pieces 101A and 101B are displaced resiliently down. As a result, the resilient forces accumulated in the two resilient contact pieces ensure a higher contact pressure.
The upper and lower resilient contact pieces 101A, 101B are held in close contact with each other over substantially the entire length from the base end portions 103A, 103B to the extending end portions 102A, 102B. The two resilient contact pieces 101A, 101B are deformed resiliently as the male tab is inserted and are displaced down together while being held in close contact with each other. The base end portions 103A, 103B are the supporting points for this resilient deformation. Thus, the deformation supporting points remain unchanged in the process of resiliently displacing the resilient contact pieces 101A, 101B, and stress is concentrated on the deformation supporting points at the base end portions 103A, 103B of the resilient contact pieces 101A, 101B.
The present invention was developed in view of the above problem and an object thereof is to prevent the concentration of a stress at resilient contact pieces.
The invention relates to a terminal fitting with a plurality of resilient contact pieces at least partly placed substantially one over another and extending in forward and backward directions. Base ends of the resilient contact pieces are held substantially in close contact with each other. However, a clearance is defined between at least parts of the resilient contact pieces when a male tab is unconnected. The male tab presses the resilient contact pieces during a connecting operation, and extends a close contact area between the resilient contact pieces from the base ends toward the extending ends.
The resilient contact pieces deform resiliently as the male tab is connected to displace portions of the resilient contact pieces corresponding to the clearance therebetween. The ends of the resilient contact pieces that are in close contact are the supporting point about which the resilient contact pieces deform. Thus, the supporting point of the resilient deformation of the resilient contact pieces is displaced toward the extending ends as the close contact area of the resilient contact pieces is extended form the base ends toward the extending ends during the connection of the male tab. Therefore, the supporting point of the resilient deformation of the resilient contact pieces is not fixed at one position, and the concentration of stress during the resilient deformation can be avoided.
A contact portion at an extending end of the resilient contact piece closest to the male tab is pressed by the male tab. Thus, the resilient contact pieces are deformed to accumulate resilient restoring forces that ensure a contact pressure between the male tab and the resilient contact pieces.
The resilient contact pieces preferably are in close contact when the male tab is connected. Further, the resilient contact pieces have the clearance when the male tab is unconnected, but are held substantially in contact with each other at a position more toward the extending ends thereof than the clearance.
At least one resilient contact may piece have a weakened portion formed by reducing a lateral cross section normal to the extending direction of the resilient contact piece. The resilient contact piece has a lower rigidity where the weakened portion is formed, and hence stress is distributed over the area where the weakened portion is formed when the resilient contact piece is deformed. As a result, stress acting on the supporting point of the resilient deformation of the resilient contact pieces is reduced.
At least one of the resilient contact pieces is curved slightly to have a concave side facing inwardly in a free state where the male tab is not connected.
A clearance narrower than the thickness of the male tab preferably is defined between a contact portion of the resilient contact piece and an opposite plate of the terminal fitting when the resilient contact pieces are in a free state.
At least one resilient contact piece comprises a curved portion extending from an extending end of a substantially flat portion. The convexly curved portion faces in a resiliently deforming direction of the plurality of the resilient contact pieces.
At least one of the plurality of the resilient contact pieces comprises an embossment for contact the male tab.
The clearance preferably opens forwardly when the male tab is unconnected.
These and other objects, features and advantages of the present invention will become more apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings. It should be understood that even though embodiments are separately described, single features thereof may be combined to additional embodiments.